The continuous trend toward the miniaturization of RF components imposes particular requirements with regard to the mutual couplings of circuit parts in the component. The distances between the circuit parts decrease as a result of a miniaturized design. As a result, undesired signal components from one part can be more easily coupled into another part. If duplexers, for example, were miniaturized without further measures, then the isolation would be impaired. Starting from a critical value for the isolation, the miniaturization would no longer be possible since the duplexer would then no longer be able to fulfill predefined requirements with regard to the isolation.
U.S. Patent Application Publication No. 2011/0254639A1 discloses arranging a capacitive element between antenna connection or receiving connection of a duplexer or between transmitting connection and receiving connection in order to reduce crosstalk.
International Patent Publication No. WO 2011/092879A1 discloses a coil at a transmitting connection. In this case, the coil is arranged on the substrate in such a way that it becomes located alongside its filter-topologically adjacent resonators.
U.S. Pat. No. 7,151,430B2 discloses a coil structure for reducing an inductive coupling. In this case, the coil has regions in which parts of the coil turn overlap other parts.
International Patent Publication No. WO 2011/101314 discloses micro acoustic filters having a Figure eight current loop.
The documents cited above specify measures for reducing electromagnetic coupling, but are technically relatively complex to realize.